Reply #64: all the indefinate article indicates to me

[Fovea]

is that there might exist other mechanisms.

Missing are the verbs 'may' or 'shall' which would indicate
IIRC, discretion or the lack thereof. In light of their abscence, it seems to me
that my premise is arguable.

Here is James Madison on the issue--

"Mr. MADISON thought it indispensable that some provision should be made for defending the Community agst. the incapacity, negligence or perfidy of the chief Magistrate. The limitation of the period of his service, was not a sufficient security. He might lose his capacity after his appointment. He might pervert his administration into a scheme of peculation or oppression. He might betray his trust to foreign powers. The case of the Executive Magistracy was very distinguishable, from that of the Legislature or of any other public body, holding offices of limited duration. It could not be presumed that all or even a majority of the members of an Assembly would either lose their capacity for discharging, or be bribed to betray, their trust. Besides the restraints of their personal integrity & honor, the difficulty of acting in concert for purposes of corruption was a security to the public. And if one or a few members only should be seduced, the soundness of the remaining members, would maintain the integrity and fidelity of the body. In the case of the Executive Magistracy which was to be administered by a single man, loss of capacity or corruption was more within the compass of probable events, and either of them might be fatal to the Republic."

Note the phrases "indespensable ... for defending the community" "And if one or a few members only should be seduced, the soundness of the remaining members, would maintain the integrity and fidelity of the body."

Madison says 'would', not 'might'. THis is a reason why executives seek (until Dubya) plausible deniability.
And, if his phrase 'defending the community' is accepted as a raison d'etre, then a failure to defend is not a matter of discretion, but an act of malfeasance.

"Ben Franklin--
Doctr. FRANKLIN mentioned the case of the Prince of Orange during the late war. An agreement was made between France & Holland; by which their two fleets were to unite at a certain time & place. The Dutch fleet did not appear... Had he been impeachable, a regular & peaceable enquiry WOULD have taken place and he WOULD if guilty have been duly punished, if innocent restored to the confidence of the public."

(emphasis mine)
Not should, not might, not could... But our old friend the A.S. verb 'willian' dressed in 18th century clothes.